The biggest enemy for outdoor athletes is not the opposing team. It is not the pitcher on the mound they are staring in the eye, or the referee making unfair calls. Their biggest enemy is the one thing they almost can't avoid: the sun.

Staying out in the midday sun for longer hours and more days than the average population, outdoor athletes are at a high risk for all skin cancers including the most harmful, melanoma. Skin cancer is the most common cancer in the United States, with more cases than all other cancers combined. One in five Americans will have skin cancer.

Olympic swimming icon Summer Sanders and MLB Hall of Famer Mike Schmidt are among the survivors of skin cancer. Now they are advocates for prevention.

A few years ago, Schmidt went to the dermatologist to investigate a mark he found on his hand. His dermatologist discovered a mole on his back that same day. A few days later, the three-time MVP and 12-time All-Star was diagnosed with Stage III Melanoma.

"Early detection is key," Schmidt said. "If I had not had early detection, I might not be sitting here right now."

Schmidt has been cancer free since 2015, but it took a team of support and a reformed relationship with the sun to return to the behind-the-spotlight life of retirement he was enjoying.

Spending decades in the sun also caught up with Sanders. The love of her sport got the best of her, as the countless days of training in the sun, with rays even stronger when reflected off a pool, did the damage.

"I didn't see myself as a candidate for this cancer," Sanders said. "Or any cancer really. ... Honestly I don't know why. I spent every waking hour outside in my backyard pool or at my club pool swimming without sunscreen. Because to me, training didn't need sunscreen. Vacation needed sunscreen."

In 2013, her husband discovered a black dot on the back of her calf and encouraged her to visit a doctor about it. A week later, she got a call urging her to come back the very next day.

Sanders had Stage I Malignant Melanoma, which was fortunately discovered very early on. She developed two more moles during the next two years, which were also detected as early as possible, thanks to her diligence.

"We are in the driver's seat of this cancer," Sanders said. "If we check ourselves and we know what our moles look like and the change of that and we look at our family members and know the change of their moles, we can then detect it early and go in to see a dermatologist to get it taken care of."

Dermatologist Darrell S. Rigel, MD, Clinical Professor of Dermatology at New York University Medical Center cites using the ABCDE's to investigate any irregular mark on your body.

A = Asymmetry. Does one side not look like the other?

B = Border irregularity. Is there a distinct border around your mark?

C = Color. The color can be light or dark, but normal moles tend to be uniform in color, while early melanoma tends to show uneven colors.

D = Diameter. Is it greater than a pencil eraser?

E = Evolving shape, size or color.

"Those are all warning signs and you really should see your dermatologist for that," Rigel said. "Checking it out is really simple if you think about it. We can look at it under a microscope and get an answer for it."

Sanders has become much more proactive in protecting herself and her two children from the sun. Amid the successful television career she has maintained since winning four Olympic medals, including two gold, she volunteers her time to educate the public on the warning signs of the disease.

Already familiar with the importance of a team, Schmidt formed a cancer game plan team with his doctors, close friends and family to get him through his diagnosis. Schmidt partnered with the Your Cancer Game Plan campaign to help provide others battling melanoma the tools and resources they need. The website has resources on how to move forward after a melanoma diagnosis has hit you, a teammate or a loved one.

"Respect the sun," said Schmidt, who also advised wearing wide-brimmed hats in addition to sunscreen. "Create a relationship with a dermatologist and see them four to five times a year."

It might be the middle of winter now, but there's never a bad time to pay attention properly protect yourself from the sun. For more information, go to SpotSkinCancer.org.